General

Question 1

BED equation

Answer 1

BED = nd (1+d/(alpha/beta))

Question 2

BED equation with proliferation

Answer 2

BED = BED - (ln2/alpha)((Ttreat-Tk)/Tpot)
Ttreat is total treatment time
Tk is treshold doubling time (onset of proliferation)
Tpot is doubling time of tumour assuming no cell loss
If Tteat< Tk, do not include correction

Question 3

EQD2 equation

Answer 3

EQD2= nd ((d+alpha/beta)/(2+alpha/beta))

Question 4

What is NTD

Answer 4

normalized total dose; like EQD2 but not necessarily for 2 Gy fractions

Question 5

where is linear quadratic model not accurate?

Answer 5

hypo-fractionation

Question 6

what does BED mean?

Answer 6

likee EQD2 but for 0 Gy fractions-infinitely many fractions

Question 7

what does it mean to ablate cell?

Answer 7

destroy it
not time for sub-lethal damage repair

Question 8

when does LQ model turn linear again?

Answer 8

dose > 7 Gy/fx

Question 9

limitations of proliferation term in BED equation

Answer 9

-does not take into account redistribution or reoxygenation
-tumor proliferation is more complex than simple exponential
-parameters vary from tumor to tumor and person to person

Question 10

most radioresistant phase of cell cycle

Answer 10

latter part of S phase- homologous recombination means there is a copy ready to go to use for repair

Question 11

most radiosensitive phase of cell cycle

Answer 11

at or near mitosis

Question 12

phases of cell cycle

Answer 12

Synthesis- DNA replication
G2 - 2nd growth phase (prepare for mitosis)
Mitosis- prophase, metaphase, anaphase, telophase)
G1-first growth phase- growth and normal metabolic roles

Question 13

OER

Answer 13

-oxygen enhancement ratio
-2-3 for x-rays
-(dose of hypoxic irradiation)/(dose of aerated irradiation) to get same amt of biologic damage

Question 14

alpha particle LET

Answer 14

100 keV/um- max cell kill-above this is wasteful

xrays are ~ 1 keV/um

Question 15

practical treshold for deterministic effect for diagnostic radiology

Answer 15

2 Gy

Question 16

skin dose vs effect

Answer 16

> 2 Gy- transient erythema
6 Gy - erythema 1-2 weeks after exposure
10 Gy- dry desquamation
15 Gy- moist desquamation

if basal cells can recover, skin effects are reversible

3-5 Gy- hair loss
-onset after 2-3 weeks
>7 Gy can be permanent hair loss

Question 17

doses for sterility

Answer 17

0.2 Gy-diminished sperm count
0.5 Gy- temporary sterility
6 Gy- sterility
3 Gy in fractions over few weeks= permanent sterility (ie fractions are worse)

one time dose:
2 Gy in women = permanent sterility
6 Gy in men = permanent sterility

Question 18

most important factor affecting lifetime attributable risk of cancer incidence and cancer mortality

Answer 18

-age of exposed individual

Question 19

carcinogenesis and hereditary effects are what type of effect?

Answer 19

stochastic

Question 20

relative risk model vs absolute risk model

Answer 20

absolute: assumes radiation produces a discrete number of cancers that is independent of spontaneous level of cancer incidence
relative: assumes radiation increases spontaneous level

-usually use relative risk model

Question 21

latency

Answer 21

-time between irradiation and appearance of malignancy
-2-25 years for leukemia
-solid tumours 5-10 years

Question 22

double dose

Answer 22

-absorbed dose to gonads of whole population that would double spontaneous mutation incidence
-current estimate is 2 Gy

Question 23

fetal dose from CT scan

Answer 23

30 mGy

Question 24

fetal dose from fluoro

Answer 24

10 mGy/min

Question 25

fetal dose from abdominal xray

Answer 25

1 mGy

Question 26

genetically significant dose

Answer 26

0.3 mGy
-index of potential genetic damage
-accounts for dose received by gonads and number of offpsring and individual is likely to produce